Hydraulic valve lifters use the engines oil pressure to expand the lifter which provides a zero valve lash clearance. This prevents the valves from tapping. When the engine is shut off, a valve and spring in the lifter keep it expanded and retain the oil within the lifter.
1. Pain that injects from your back or neck to your hand or foot. Shooting or cutting pain is what pain from a herniation feels like. If this pain goes all the way to your hand or foot then this possibly a disc herniation. Pain that ends before crossing your knee or elbow is most likely to be referred pain.
If the herniated disc material impinges on a spinal nerve root as the nerve root exits the spine, it can cause radiating pain down the back of the thigh and possibly into the calf or foot on one side of the body.